Thermoelastic-damping noise from sapphire mirrors in a fundamental-noise-limited interferometer

We report the first high-precision interferometer using large sapphire mirrors, and we present the first direct, broadband measurements of the fundamental thermal noise in these mirrors. Our results agree well with the thermoelastic-damping noise predictions of Braginsky, et al. [Phys. Lett. A 264, 1(1999)] and Cerdonio, et al.[Phys. Rev. D 63, 082003 (2001)], which have been used to predict the astrophysical reach of advanced interferometric gravitational wave detectors.Comment: 4 pages, 2 figure

Possible Observational Criteria for Distinguishing Brown Dwarfs from Planets

The difference in formation process between binary stars and planetary systems is reflected in their composition as well as their orbital architecture, particularly orbital eccentricity as a function of orbital period. It is suggested here that this difference can be used as an observational criterion to distinguish between brown dwarfs and planets. Application of the orbital criterion suggests that with three possible exceptions, all of the recently-discovered substellar companions discovered to date may be brown dwarfs and not planets. These criterion may be used as a guide for interpretation of the nature of sub-stellar mass companions to stars in the future.Comment: LaTeX, 11 pages including 2 figures, accepted for publication in the Astrophysical Journal Letter

A basic lock-in amplifier experiment for the undergraduate laboratory

We describe a basic experiment for the undergraduate laboratory that demonstrates aspects of both, the science and the art of precision electronic measurements. The essence of the experiment is to measure the resistance of a small length of brass-wire to high accuracy using a simple voltage divider and a lock-in amplifier. By performing the measurement at different frequencies and different drive currents, one observes various random noise sources and systematic measurement effects

Particle Dynamics in Damped Nonlinear Quadrupole Ion Traps

We examine the motions of particles in quadrupole ion traps as a function of damping and trapping forces, including cases where nonlinear damping or nonlinearities in the electric field geometry play significant roles. In the absence of nonlinearities, particles are either damped to the trap center or ejected, while their addition brings about a rich spectrum of stable closed particle trajectories. In three-dimensional (3D) quadrupole traps, the extended orbits are typically confined to the trap axis, and for this case we present a 1D analysis of the relevant equation of motion. We follow this with an analysis of 2D quadrupole traps that frequently show diamond-shaped closed orbits. For both the 1D and 2D cases we present experimental observations of the calculated trajectories in microparticle ion traps. We also report the discovery of a new collective behavior in damped 2D microparticle ion traps, where particles spontaneously assemble into a remarkable knot of overlapping, corotating diamond orbits, self-stabilized by air currents arising from the particle motion

Studies of Autumn calving suckler cows, bulls at pasture and winter grazing

End of project reportMost beef and dairy cows are spring calving leading to distinct seasonality of supply. Calving a proportion of the beef herd in the autumn would lead to a more uniform annual supply of cattle for slaughter and potentially increase the proportion of grazed grass in the diet of the suckler progeny. Autumn calving sucklers also facilitate the use of AI, which should enhance the product quality. This project aimed to address the technical aspects of autumn calving sucklers, which differ from those of spring calvers. The currently available international energy models were evaluated for autumn calving lactating suckler cows using the type of cow typically found in Irish suckler herds (Experiment 1). The winter accommodation of the suckler cow and calf unit and its impact on cow reproductive performance was evaluated (Experiment 2). The final part of the project evolved into component studies to determine the effect of supplementary feed on the performance of grazing bulls (Experiment 3), and the consequences of weanling cattle grazing pasture in winter as an alternative to housing them in winter (Experiments 4 to 7)

Macroscopic coherence effects in a mesoscopic system: Weak localization of thin silver films in an undergraduate lab

We present an undergraduate lab that investigates weak localization in thin silver films. The films prepared in our lab have thickness, $a$, between 60-200 \AA, a mesoscopic length scale. At low temperatures, the inelastic dephasing length for electrons, $L_{\phi}$, exceeds the thickness of the film ($L_{\phi} \gg a$), and the films are then quasi-2D in nature. In this situation, theory predicts specific corrections to the Drude conductivity due to coherent interference between conducting electrons' wavefunctions, a macroscopically observable effect known as weak localization. This correction can be destroyed with the application of a magnetic field, and the resulting magnetoresistance curve provides information about electron transport in the film. This lab is suitable for Junior or Senior level students in an advanced undergraduate lab course.Comment: 16 pages, 9 figures. Replaces earlier version of paper rejected by Am. J. Phys. because of too much content on vacuum systems. New version deals with the undergraduate experiment on weak localization onl

Enhanced photothermal displacement spectroscopy for thin-film characterization using a Fabry-Perot resonator

We have developed a technique for photothermal displacement spectroscopy that is potentially orders of magnitude more sensitive than conventional methods. We use a single Fabry-Perot resonator to enhance both the intensity of the pump beam and the sensitivity of the probe beam. The result is an enhancement of the response of the instrument by a factor proportional to the square of the finesse of the cavity over conventional interferometric measurements. In this paper we present a description of the technique, and we discuss how the properties of thin films can be deduced from the photothermal response. As an example of the technique, we report a measurement of the thermal properties of a multilayer dielectric mirror similar to those used in interferometric gravitational wave detectors

Teachers developing assessment for learning: impact on student achievement

While it is generally acknowledged that increased use of formative assessment (or assessment for learning) leads to higher quality learning, it is often claimed that the pressure in schools to improve the results achieved by students in externally-set tests and examinations precludes its use. This paper reports on the achievement of secondary school students who worked in classrooms where teachers made time to develop formative assessment strategies. A total of 24 teachers (2 science and 2 mathematics teachers, in each of six schools in two LEAs) were supported over a six-month period in exploring and planning their approach to formative assessment, and then, beginning in September 1999, the teachers put these plans into action with selected classes. In order to compute effect sizes, a measure of prior attainment and at least one comparison group was established for each class (typically either an equivalent class taught in the previous year by the same teacher, or a parallel class taught by another teacher). The mean effect size was 0.32

A basic Michelson laser interferometer for the undergraduate teaching laboratory demonstrating picometer sensitivity

We describe a basic Michelson laser interferometer experiment for the undergraduate teaching laboratory that achieves picometer sensitivity in a hands-on, table-top instrument. In addition to providing an introduction to interferometer physics and optical hardware, the experiment also focuses on precision measurement techniques including servo control, signal modulation, phase-sensitive detection, and different types of signal averaging. Students examine these techniques in a series of steps that take them from micron-scale sensitivity using direct fringe counting to picometer sensitivity using a modulated signal and phase-sensitive signal averaging. After students assemble, align, and characterize the interferometer, they then use it to measure nanoscale motions of a simple harmonic oscillator system as a substantive example of how laser interferometry can be used as an effective tool in experimental science

Risk of cancer following primary total hip replacement or primary resurfacing arthroplasty of the hip : A retrospective cohort study in Scotland

Acknowledgements: We are grateful to Lee Barnsdale, Doug Clark, and Richard Dobbie for advice and assistance with data preparation before analysis, and to the three anonymous referees for their helpful comments and suggestions.Peer reviewedPublisher PD